1. Field of the Invention
The present invention relates to information retrieval systems and particularly to such systems for providing a retrievable updateable display of a permanent microfilm record.
2. Description of the Prior Art
Information retrieval systems employing permanent microfilm records are well known. An example of such prior art microfilm record systems are the automatic microfilm record search systems in use today in many libraries for storing vast quantities of information. However, although microfilm storage of information is economical and efficient, it becomes inefficient for storage of bulk records in which certain portions thereof are changed on a fairly frequent basis. An example of such bulk records would be the patient records of a hospital where the addresses and other vital statistics relevant to the patients may change on a fairly frequent basis.
Gas panel display devices, and particularly plasma tubes, are well known in the art. An example of such prior art plasma tube displays is the Orion-60 microprocessor controlled display terminal manufactured by Magnavox. This prior art terminal features interactive graphic and alphanumeric displays. Another prior art plasma tube display device is the Magnavox model 10,000 microfiche projection device. Such a prior art device employes a slide projector with folded optics, computer control selection of the display and a composite superimposed display.
A plasma tube, however, is not the first such prior art device to enable superimposed displays. Rather, such superimposed displays are well known, such as disclosed in U.S. Pat. No. 3,728,712 which discloses a video file superposition system in which two video signals are superposed on a video signal, similar to keying in information, to update a video file record. Similarly, U.S. Pat. No. 3,941,926 discloses a system employing computer control of a plasma display to provide a composite display from plural video cameras. U.S. Pat. No. 3,883,861 discloses a prior art CRT/beam splitter system for providing a combined map image projection which is updateable by a computer generated image. Similarly, U.S. Pat. Nos. 3,906,197; 2,972,703; 3,125,741; 3,498,692; 3,651,509; 3,801,862 and 3,851,211 all disclose plasma tube display systems. However, none of these prior art systems known to applicant is capable of providing a substantially simultaneous gas panel display of corresponding updated stored information visually supplanted in the composite visual display with respect to the predetermined portions of the selectably retrieved projected permanent microfilm record. Thus, these prior art systems known to applicant do not provide an efficient system which allows a large data bank to be kept up to date efficiently and economically through means of keeping the source data base on permanent microfilm while keeping revisions to the microfilm images in a bulk digital memory and thereafter generating an updated microfilm-plasma composite image whenever a revised record is requested. These disadvantages of the prior art are overcome by the present invention.